CRTH2 is G-protein coupled receptor expressed on Th2 cells, eosinophils and basophils that mediates the effects of prostaglandin D2 (PGD2). CRTH2 is a therapeutic target for certain diseases including allergic diseases, such as asthma, exercise induced asthma, allergic rhinitis, atopic dermatitis, allergic conjunctivitis, as well as Churg-Strauss syndrome, sinusitis, basophilic leukemia, chronic urticaria and basophilic leukocytosis. Pyrimidin-5-yl acetic acid derivatives including those described in international patent application publications WO 2004/096777 (published Nov. 11, 2004) or in WO 2005/073234 (published Aug. 11, 2005) are effective antagonists of CRTH2 and promising candidates for use in the treatment of CRTH2-related diseases or disorders. Improvements including without limitation extending pharmacological effective lives and/or decreasing metabolic liabilities in vivo, of therapeutic pyrimidin-5-yl acetic acid derivatives are sought.